THE NATURAL HABITAT of thick, gray jersey used to be running trails and dorm room sofas. But thanks to designers such as fleece-loving dress sculptor Norma Kamali and indie darling Alexander Wang (who reinvented work-it-out wear as party-worthy dresses and pants this season), the charcoal cotton now punches up pieces better suited to a K Street club than kickboxing class. “It feels a little like cheating,” says Marlene Hu Aldaba, who’s stocked her Georgetown boutique, Hu’s Wear, with sports-inspired knits by Isabel Marant. “You get all the comfort and relaxed feel of sweats, but in a sophisticated form.”

» ATHLETIC STAR: Balance a pretty floral sundress with a cheeky (and chill-chasing) cover-up. Parameter print dress ($158, Ginger, 7114 Bethesda Ave., Bethesda; 301-664-9242) and Norma Kamali athletic bat-wing cardigan ($18)

» LEADING EDGE: A swingy vest toughens up, thanks to shoulders trimmed with silvery studs. Aiko vest ($198) and Vince dress ($210, both Neiman Marcus, Mazza Gallerie, 5300 Wisconsin Ave. NW; 202-966-9700), with Calvin Klein sandals ($128, Bloomingdale’s, 5300 Western Ave., Chevy Chase; 240-744-3700)

» WINNING PICK: Textured jersey goes upscale in a sleekly draped day dress. Rebecca Taylor dress ($275) and Lily Posh chain and pearl necklace ($140, both Cusp)

» GOOD SPORT: Comfy cotton lends a tailored twist to a classic blazer. Blazer ($59.50, Gap stores), Diane von Furstenberg blouse ($245) and pencil skirt ($185, both Bloomingdale’s) and Dolce Vita pumps ($165, Cusp)

» TOP SCORE: Swap a trad blouse for a shrunken, short-sleeved sweatshirt. Alternative Apparel the Gym Rat eco-fleece crew ($17), Marc by Marc Jacobs skirt ($328) and Elizabeth & James gold wedges ($270, both Cusp, 3030 M St. NW; 202-625-0898)

Photos by Marge Ely